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Abstract

Nucleic acid therapy holds real promise to offer less severe (lower side effects) as a treatment for life threatening and difficult to treat diseases such as cancer, heart disease or Alzheimer\'s disease. Theranostic nanomaterials that combine diagnostic imaging and therapeutic delivery, have potential to minimize the amount of time and dosage required for the treatment. This is achieved via delivery of nanoparticles that carry therapeutic payload as well as imaging agents; these agents need to circulate in the body longer due to its (larger) size and selectively accumulate in the tumor regions through the enhanced permeability and retention (EPR) effect. We have designed novel lanthanide (Gd, Tb or La) containing polymers with oligoethyleneamine and lanthanide chelating units to incorporate DNA binding and imaging agent functionality. Protonable amines along the polymer backbone electrostatically interact with DNA and compact it into a nanoparticle. These nanoparticles can be imaged both in vivo (Gd analogues, magnetic resonance imaging) and intracellularly (Tb chelation, fluorescence spectroscopy). Polymers were synthesized via step-growth polymerization to achieve a degree of polymerization of 18-24 for different analogues with varying amine number (three to six, N3-N6) along the backbone. Dynamic light scattering performed on the polyplexes (polymer-DNA complexes) indicate that they are in nanometer size range (50-80nm). All the polymers used to form polyplexes exhibited low toxicity to cultured human Glioblastoma cells (U-87) and showed variable transfection efficiency dependent on structure, comparable to G4 (sold as Glycofect"), a commercial transfection agent previously developed in our lab. This dissertation describes the first studies by the Reineke lab to monitor polyplex formation and destabilization using lanthanide resonance energy transfer (LRET). Polyplexes were formulated with Tb chelated N5 polymer and tetramethyl rhodamine (TMR) labeled pDNA, which are "LRET pairs". We observed decrease in luminescence intensity of Tb polymer (donor) in close proximity of TMR DNA (acceptor) in an intact polyplex at different N/P ratios. However, upon destabilization of polyplexes by addition of salt or heparin solution, the increase in distance between donor and acceptor resulted in increase in the luminescence intensity of Tb polymer. With the LRET technique, we are able to monitor formation and destabilization of polyplexes by monitoring change in luminescence of the donor chromophore (Tb).Polyplexes formulated with non-paramagnetic analogues (La chelated) of N4, polyethyleneimine (PEI) and G4 were studied using NMR to quantify free vs. bound polymer in a formulation. The amount of free polymer was measured by integrating the broad resonances from nanometer-sized particles (polyplexes) with narrow peaks from free polymer chains. This was supported by using an internal reference method to quantify free polymer amount from known internal reference concentration. We observed an increase in the amount of free polymer with N/P ratio for all three systems and both the methods showed comparable results.